Properties of the Number 646

Six Hundred Forty-Six

Basics

Value: 645 → 646 → 647

Parity: even

Prime: No

Previous Prime: 643

Next Prime: 647

Digit Sum: 16

Digital Root: 7

Palindrome: Yes

Factorization: 2 × 17 × 19

Divisors: 1, 2, 17, 19, 34, 38, 323, 646

Polygonal

Triangular: No

Square: No

Pentagonal: No

Hexagonal: No

Heptagonal: No

Tetrahedral: No

Today's Target

2730 Try Today's Challenge

Representations

Binary: 1010000110

Octal: 1206

Duodecimal: 45A

Hexadecimal: 286

Square: 417316

Square Root: 25.41653005427767

Classification

Fibonacci: No

Bell Number: No

Factorial Number: No

Regular Number: No

Perfect Number: No

Special

Kaprekar Constant: No

Munchausen Constant: No

Armstrong Number: No

Kaprekar Number: No

Catalan Number: No

Vampire Number: No

Taxicab Number: No

Super Prime: No

Friedman Number: No

Fermat Number: No

Cullen Number: No

OEIS Sequences

Hertzsprung's problem: ways to arrange n non-attacking kings on an n X n board, with 1 in each row and column. Also number of permutations of length n without rising or falling successions. A2464

Number of Carmichael numbers (A002997) less than 10ⁿ. A55553

a(n) is the number of subsets of {1,...,n} containing no solutions to x+y=z with·and y distinct (one version of "sum-free subsets"). A85489

Palindromic in bases 9 and 10. A29965

Numbers that are the sum of 7 positive 5th powers. A3352

First spoke of a hexagonal spiral. A56105

a(n) = 2·n² - 2. A54000

Number of compositions of n such that every part occurs with the same multiplicity. A98504

Ordered perimeters of primitive Pythagorean triangles. A24364

Numbers that are the sum of 11 positive 7th powers. A3378